The prophylactic effect of a teat sealer on bovine mastitis during the dry period and the following lactation

Aim. To determine the prophylactic efficacy of a teat sealer, administered at drying off, in reducing new intramammary infections in the dry period and the following lactation.Methods. A total of 528 cows with late lactation somatic cell counts < 200 000 cells/ml was identified in three commercial herds. Of these, bacteriological examination showed 482 cows were uninfected in all four quarters and 46 were infected in only one quarter. At drying off, uninfected quarters were randomly allocated to the following treatments: no infusion (negative controls), infusion with a bismuth subnitrate based teat sealer, infusion with teat sealer + antibiotic, or infusion with a cephalonium-based dry cow antibiotic (positive control). New infections were identified during the dry period by periodic udder palpations and at calving by bacteriological culture.Results. All three infused treatments reduced the incidence of new intramammary infections due to Streptococcus uberis, both during the dry period and at calving, by about 90% (p < 0.01 ). The majority of the infections were due to Streptococcus uberis. For all treatments, a 50% lower incidence of clinical mastitis over the first 5 months of the ensuing lactation was reported by farmers. X-ray imaging of 19 teats showed that the teat sealer material was retained, at least in part, in the lower teat sinus over about 100 days of the dry period.Conclusions. Closure of the teat canal from day one of the dry period as achieved by the teat sealer was as effective in reducing new dry period infections as the infusion of a long-acting dry cow antibiotic formulation. The lower incidence of new infections in the ensuing lactation among the infused quarters implies that fewer subclinical infections persisted from the dry period. Use of teat sealers at drying off appears to offer the same prophylactic efficacy as the dry cow antibiotic approach.